This invention relates to an integrated circuit for liquid crystal display, for driving a dot matrix type liquid crystal display and, more particularly, to an improvement in an arrangement of output terminals for outputting a plurality of pixel or picture element drive signals in a parallel fashion.
FIG. 1 is a schematic illustration of a liquid crystal (LC) display apparatus. In the figure, reference numeral 51 designates a liquid crystal display device, 52 a semiconductor integrated circuit, for example, a large scale integration (LSI) for driving the LC display device, and 53 a printed wiring board, i.e., printed wiring substrate. The output signal terminals (not shown) of board 53 and the electrode terminals of the LC display device 51 are connected by conductive wires (not shown).
When an LC display device with picture elements (pixels) arrayed in a matrix fashion, called a dot matrix type LC display device, is used, LSI 52 is so constructed as to produce a plurality of pixel drive signals in a parallel fashion. An array of external terminals of a conventional LSI is illustrated in FIG. 2. In the figure, reference numeral 61 designates a package, Pl to P19 pixel drive output terminals for outputting the pixel drive signals, and Pc control terminals for control signal. Output terminals P1 to P19 are numbered 1, 2, 3, . . . , 19 in a direction, respectively.
The drive signals output from the output terminals P1 to P19 of LSI 52 are applied to those pixels of the pixel array of LC display device 51 which correspond to the output terminals P1 to P19 of LSI 52.
A conventional structure of dot matrix type LC display device 51 is illustrated in FIG. 3. The LC display device 51 is comprised of a pair of transparent substrates made of, for example, glass, a plurality of transparent electrodes for pixel drive, which are arrayed on the inner surfaces of the transparent substrates, liquid crystal filled in the space between the paired transparent substrates, and light directing boards laid on the outer surfaces of the transparent substrates. The center portion of the transparent substrates constitutes a display section 71. The extended portions of the transparent electrodes form a wiring section 72 and electrode terminal section 73. In display section 71, the transparent electrodes constituting common electrodes (in this example, five electrodes) extend in the horizontal direction of the substrates. The transparent electrodes constituting segment electrodes (in this example, twenty electrodes) are arrayed in the vertical direction of the substrates. Electrode terminals 73.sub.1 to 73.sub.20 are connected to the segment transparent electrodes, located at the ends of the substrates in the horizontal direction, and numbered 1, 2, 3, . . . , 20 in the horizontal direction, respectively. These electrode terminals are grouped into array-portions. The array-portions are alternately arranged on both sides of the substrate. The terminals in each array-portion are successively arrayed in the order of the terminal numbers.
When LC drive LSIs 52 with the external terminal array shown in FIG. 2 are used to drive dot matrix type LC display devices 51 with the electrode terminal array shown in FIG. 3, the wiring pattern of the printed wiring board used for carrying the LSIs 52 is illustrated in FIG. 4. The output signal terminals of printing wiring substrate 53 are located at the ends thereof in the horizontal direction, and grouped into array portions 82. The output terminals of each LSI 52 for outputting pixel drive signals are connected to the corresponding array-portions of the output signal terminal of substrate 53, via printed wirings 81 for leading the drive signals. However, array-portions 82 of substrate 53 are alternately located at both sides of the printed wiring board, and the order of the terminal numbers in each array-portion 82 is the same as that in the corresponding array-portion of the electrode terminals of LC display device 51. Consequently, the order of the terminal numbers of half of the output terminals of each LSI 52 is opposite to the order of the terminal numbers of the output terminals of printed wiring board 53. If those terminals oppositely arrayed are connected on the same surface of board 53, wirings 81 connecting the oppositely arrayed terminals cross with each other. In order to avoid this problem conventionally, the printed wirings are formed on both surfaces of printed wiring board 53, as shown in FIG. 4. The printed wires formed on the back surface are indicated by dotted lines. The wirings formed on both surfaces are connected via contact-holes 83.
Drive signals are applied, in a time division manner, to the electrode terminals 73.sub.1 to 73.sub.20 of LC display device 51. The LC drive circuit (not shown) for generating the drive signal is mounted on printed wiring board 53. The printed wirings (not shown) for supplying the drive signals, and their output signal terminals (not shown) are provided on printed wiring board 53.
If such a layout of wirings is employed for avoiding the crossing of wirings, a number of contact-holes 83 must be formed. As a result, the cost to manufacture printed wiring board 53 is increased, and the reliability of the wiring connection is reduced.
In an LC display device 51 as shown in FIG. 3, the electrode terminals in each array-portion are successively arrayed in the order of terminal number in the horizontal direction of the display device. Therefore, as the number of electrode terminals is increased, the wiring portion 72 between electrode terminal section 73 and display section 71 occupies a large area on the chip. As a result, the ratio of the occupied area of display 71 in LC display device is reduced. The result is that the manufactured displayed image is unreadable, and the ineffective portion of the liquid crystal layer which does not contribute to the display, is increased.